The principal source of electricity for spacecraft is the solar array, which converts sunlight into direct electrical current. In conjunction therewith rechargable batteries are used to provide the necessary electrical current during those periods when the satellite is on the dark side of its orbit around the earth and, consequently, the solar array is shielded from sunlight and unable to produce electrical current.
The electrical power generated by the solar array is distributed within the spacecraft over the power bus, an electrical wiring system, not only to the spacecraft's electronic apparatus, but to the rechargable battery as well, to replenish any expended electrical power. In the re-charge mode, the battery, thus, also effectively functions as part of the system's electrical load.
Different satellite missions demand different electrical power supply requirements. For example, a satellite operating in geosynchronous orbit is exposed to sunlight for approximately twenty two and one half hours and to darkness for one and one half hours in a continuing sequence. However, in a low earth orbit, at an altitude of less than five thousand miles, the satellite is exposed to sunlight for only sixteen minutes and then to darkness for sixteen minutes in continuing sequence. The power supply systems for the respective missions are consequently different and are not interchangeable.
Heretofore solar array power supply systems were custom designed for specifice missions with the attendent development and production costs. Hence, to control costs a need arises for power supply systems the are modular and can readily be used for different satellite missions.
An object of the present invention is to provide a power supply system having modularity; one useful in different missions with different power requirements that can be adapted with only routine and minor changes. Such routine changes and adaptations would involve, as example, selection of the number of solar panels that together form the solar array to meet the different requirements.
A further object of the invention is to provide a digitized modular power subsystem without adding unnecesary weight or expense to a given satellite.